cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A309835 Numbers k such that k + phi(k) is a repunit.

Original entry on oeis.org

5798663, 5555564201311, 5555574497311, 5555593942711, 66815976110703, 69437045907973255623
Offset: 1

Views

Author

Giovanni Resta, Aug 19 2019

Keywords

Comments

Also in the sequence is 555555555555555555555556288388841217550575591423513701223. - Robert Israel, Aug 20 2019
The number 5975946235638859341313216528710061511 is also in the sequence. - Daniel Suteu, Aug 22 2019

Examples

			5798663 is a terms since phi(5798663) = 5312448 and 5798663 + 5312448 = 11111111.

Crossrefs

Subsequence of A116018.
Cf. A000010, A002275, A121048, A244444.

Programs

  • PARI
    isok(k) = my(d=digits(k+eulerphi(k))); vecmin(d)==1 && vecmax(d)==1; \\ Daniel Suteu, Aug 22 2019

Extensions

a(5) from Daniel Suteu confirmed by Max Alekseyev, Oct 25 2023
a(6) from Max Alekseyev, Nov 30 2023

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